JPH0553414B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an audio communication device that transmits an audio signal and a control signal via the same transmission path.

[Prior Art] In conventional digital cell call communication, a binary data control signal for controlling communication and an audio signal for communication are transmitted in a time-division manner using the same transmission path.

FIG. 4 is a timing chart showing an example of this communication. The sending side first calls the receiving side and sends a communication start data signal 3 to start communication.
1, transmits the audio signal 32, and then, when the communication ends, transmits the communication end data signal 3.
Send 3. Here, communication start data signal 31
The communication end data signal 33 is, for example, an 8-bit binary data signal, and each signal 31, 33 is a signal representing a specific code such as "110101", "101011", etc., respectively. On the other hand, when the receiving side receives the communication start data signal 31, it turns on the audio output switch that switches whether or not to output the received audio signal 32 to audio output devices such as speakers, earphones, and headsets. The audio signal 32 received following the communication start data signal is output to the audio output device. Next, when the communication end data signal 33 is received at the end of the communication, after turning off the audio output switch, the receiving side recognizes that the communication has ended and receives the communication start data signal 31. Performs processing on the receiving side, such as processing to prepare for.

[Problems to be Solved by the Invention] However, in the conventional communication system described above, the audio output switch is turned off after receiving the communication end data signal 33, so that the communication end data, which is a binary data signal, is turned off. There is a problem in that the signal 33 is output as a sound to the audio output device, and the operator therefore hears the data signal 33 as a harsh sound.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an audio communication system in which a control signal indicating the end of audio signal communication is not output as sound to an audio output device when the communication ends.

[Means for Solving the Problems] A voice communication system according to the present invention includes a transmitting device and a receiving device for transmitting a voice signal and a control signal via the same transmission path. The transmitting device includes transmitting means for transmitting a specific control signal that continues for a predetermined period of time when the transmission of the audio signal ends, and the receiving device transmits the audio signal and control signal received from the transmitting means via the transmission path. a switch for switching whether or not to output the audio signal and control signal received by the receiving means to the audio output device; The apparatus is characterized by comprising a control means for turning off the switch based on a control signal.

[Operation] In the voice communication system configured as described above, the transmitting means of the transmitting device transmits a specific control signal that continues for a predetermined period of time at the end of transmitting the voice signal.

On the other hand, the receiving means of the receiving device receives the audio signal and control signal received from the transmitting means via the transmission path, and the control means receives the specific signal received by the receiving means. The switch is turned off based on the control signal. Therefore, when the communication of the audio signal ends, the control signal indicating the end of the communication is prevented from being output as a harsh sound to the audio output device.

[Embodiment] FIG. 1 is a block diagram of a digital cell call communication system that is an embodiment of the present invention.

In this communication system, the transmitting device sends, for example, +
The audio end signal 34 having the H level of the binary data signal of 5V is outputted continuously for a predetermined time t0.Meanwhile, when the receiving device receives the audio end signal 34, it turns off the audio output switch 25 and outputs the audio end signal 34 that continues for a predetermined time t0. Communication end data signal 33 is sent to speaker 27
The feature is that it stops being output.

In the transmitter 100 shown in FIG. 1, the audio input to the microphone 1 is converted into an audio signal, and then output to the transmitter 5 via the amplifier 2, the b side of the switch 3, and the FM modulator 4. The transmitter 5 outputs an FM radio signal of the audio signal via the antenna 6.

The control circuit 10 is a control circuit that controls the operation of the changeover switch 3, FM modulator 4, and transmitter 5 of the transmitter 100, and stores, for example, a central processing unit that performs control processing and a control program.
It consists of ROM and RAM used as a working area during control processing. Control circuit 1
0 is connected to one end of each of a communication start switch 11 for instructing the start of communication and a communication end switch 12 for instructing the end of communication, and the other end of each switch 11, 12 is connected to ground. Ru. When the communication start switch 11 is turned on, the control circuit 1
0, switch the changeover switch 3 to the a side,
Sets the FM modulator 4 to FSK signal mode, turns on the transmitter 5, and instructs the signal generation circuit 13 to output a communication start data signal 31 for starting communication after calling the receiving device 200. After transmitting the communication start data signal 31, the switch 3 is switched to the b side, and the FM modulator 4 is set to the audio FM signal mode, thereby transmitting the audio signal to the receiving device 200 using the microphone 1. be able to. Next, communication end switch 1
2 is turned on, the control circuit 10 switches the changeover switch 3 to the a side and turns the FM modulator 4 on.
Instructs the signal generating circuit 13 to set the FSK signal mode and output the audio end signal 34 indicating the end of the audio signal, and also instructs the signal generating circuit 13 to output the communication end data signal 33 indicating the end of communication. 13, and each of the above signals 34, 33
After this is transmitted, the power to the transmitter 5 is turned off.

When instructed by the control circuit 10 to output the communication start data signal 31, the audio end signal 34, and the communication end data signal, the signal generation circuit 13 generates a binary data signal of, for example, 8 bits "110101". , an H level signal for a predetermined time t0, for example 20 milliseconds, and an 8-bit "101011" binary data signal are output to the FM modulator 4 via the a side of the changeover switch 3.

In the FSK signal mode, the FM modulator 4 performs FSK modulation on the carrier wave with a binary data signal or an H level signal input from the signal generation circuit 13, and transmits an FSK signal having a frequency 1 and a frequency 2 higher than frequency 1. On the other hand, in audio FM signal mode, the carrier wave is FM modulated by the audio signal input from microphone 1 through amplifier 2, and the frequency (1 +
2)/2, the maximum frequency deviation ±(2−
1) Output the audio FM signal FM modulated by /2 to the transmitter 5. FSK corresponding to this FM modulator 4
The frequency modulation device for signals and audio signals is disclosed in detail in the specification of the invention entitled ``Frequency Modulation Device'' filed by the applicant on October 19, 1988.

The transmitter 5 receives FSK input from the FM modulator 4.
The signal or audio FM signal is transmitted to the receiving device 200 via the antenna 6 using a carrier wave having a predetermined radio frequency.

In the receiving device 200 of FIG.
The signal received via the FM demodulator 22 is outputted to the FM demodulator 22 after being subjected to predetermined processing such as amplification and conversion to an intermediate frequency in the receiver 21 . FM
The demodulator 22 demodulates the input signal into FM and outputs it to the signal detection circuit 23, and also outputs it to the speaker 2 via the audio output switch 25 and the amplifier 26.
7 is output.

The signal detection circuit 23 detects that the input signals are the communication start data signal 31, the voice end signal 34,
Then, it is detected whether or not the communication end signal 33 is received. The signal detection circuit 23 detects the communication start data signal 31
When the audio output switch 25 is detected, the audio output switch 25 is turned on via the control circuit 24, and then the audio end signal 3 is output.
4 is detected, the audio output switch 25 is turned off via the control circuit 24, and furthermore, when the communication end data signal 33 is detected, the detection signal is output to the control circuit 24, and the control circuit 24 confirms that the communication has ended. The receiving device performs processing such as processing to prepare for receiving the communication start data signal 31. Note that after detecting the H level signal for the predetermined time t0, when the communication end data signal 33 cannot be detected after a predetermined time, for example, 5 milliseconds,
The control circuit 24 determines that the H level signal is an erroneous signal due to noise, and turns on the audio output switch 25. Here, the signal detection circuit 23 detects the time t0
When receiving H level signals continuous by ±20%, it is determined that the audio end signal 34 has been received, and the detection signal is output to the control circuit 24.

Note that the control circuit 10 and signal generation circuit 13 of the transmitting device 100, and the signal detection circuit 23 and control circuit 24 of the receiving device 200 are each preferably configured with a HD637B01 type CPU manufactured by Hitachi, Ltd.

The operation of the communication system configured as described above will be explained with reference to timing charts shown in FIGS. 2 and 3.

First, as shown in FIG. 2, in the receiving device 200, following a communication start data signal 31, an audio signal 32, an audio end signal 34, and a communication end signal 3 are transmitted.
3 is received, when the signal detection circuit 23 detects the communication start data signal 31, it turns on the audio output switch 25 via the control circuit 24, thereby causing the subsequently received audio signal 32 to become an audio signal. The signal is output to a speaker 27 via an output switch 25 and an amplifier 26. Next, when the voice end signal 34 is detected, the signal detection circuit 23 turns off the voice output switch 25 via the control circuit 24, thereby causing the communication end data signal 33 received subsequent to the voice end signal 34 to be turned off. is prevented from being output to the speaker 27. Further, when the communication end data signal 33 is detected, the detection signal is output to the control circuit 24, and the control circuit 24 recognizes that the communication has ended and enters a preparation state for receiving the communication start data signal 31. Performs processing of the receiving device, such as processing.

Further, as shown in the timing chart of FIG. 3, while receiving the audio signal 32, the transmitting device 1
If a continuous H level signal for a predetermined time t0 is received, which is noise that is not transmitted from 00 to 25 is turned off, but as shown in FIG. 3, when the communication end data signal 33 cannot be detected after a predetermined time of, for example, 5 milliseconds, the control circuit 24 determines that the H level signal is an erroneous signal due to noise. Then, turn on the audio output switch 25. Other operations are similar to those shown in FIG. 2 above. As described above, H that continues for a predetermined time t0
If the communication end data signal is not received within a predetermined time after receiving the level signal, the audio output switch 24 is restored from off to on, and the noise that is not transmitted from the transmitter 100 continues for the predetermined time t0. Even when a high-level signal is received, it is possible to prevent a malfunction in which communication is terminated and audio signals cannot be received.

As explained above, the communication end data signal 33
Immediately before the high voltage of the binary data signal, for example +5V,
On the other hand, the receiving device outputs the audio end signal 34 for a predetermined time t0 having a certain level.
is received, the audio output switch 25 is turned off to prevent the communication end data signal 33 from being output to the speaker 27, which is unpleasant to the operator.

In the embodiments described above, the transmitting device 100 transmits the communication end data signal 33 following the voice end signal 34, but the present invention is not limited to this. Only the voice end signal 34 is transmitted, and the receiving device 200 When the end signal 34 is received, the audio output switch 2
The predetermined processing for terminating the communication may be performed together with the turning off of the switch 5. In this case, it is not possible to avoid malfunctions caused by noise signals as described with reference to the timing chart of FIG. 3 above.

In the above embodiment, the audio end signal 34
is assumed to be an H level signal that continues for a predetermined time t0, but is not limited to this, and may be a signal of a predetermined level such as an L level or an intermediate level between an H level and an L level that continues for a predetermined time.

Although the above embodiment describes an example of a one-way wireless communication system, the present invention is not limited to this, and the present invention can be broadly applied to other communication systems such as full-duplex communication, half-duplex communication, and wired communication system. Can be applied.

[Effects of the Invention] As described in detail above, according to the present invention, after the transmitting device transmits a control signal of a predetermined level that continues for a predetermined period of time at the end of transmission of an audio signal, the control means of the receiving device controls the control signal from the transmitting device. A control signal indicating the end of the communication when the communication of the audio signal ends by turning off a switch that switches whether or not to output the audio signal to the audio output device when the transmitted control signal is received. This has the advantage that it is possible to prevent the sound from being output to the audio output device as a harsh sound.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a digital cell call communication system that is an embodiment of the present invention, FIGS. 2 and 3 are timing charts showing the operation of the communication system of FIG. 1, and FIG. 4 is a conventional digital cell call communication system. 3 is a timing chart showing the operation of a communication system. 1...Microphone, 2...Amplifier, 3...Switch, 4...FM modulator, 5...Transmitter, 6
...Antenna, 10...Control circuit, 11...Communication start switch, 12...Communication end switch, 13
... Signal generation circuit, 20 ... Antenna, 21 ...
Receiver, 22...FM demodulator, 23...Signal detector, 24...Control circuit, 25...Audio output switch, 26...Amplifier, 27...Speaker, 31...
...Communication start data signal, 32...Audio signal, 33
...Communication end data signal, 34...Audio end signal, 100...Transmitting device, 200...Receiving device.

Claims (1)

[Claims] 1. In a voice communication system comprising a transmitting device and a receiving device for transmitting a voice signal and a control signal via the same transmission path, the transmitting device transmits a predetermined signal at the end of transmitting the voice signal. The receiving device includes a transmitting means for transmitting a specific control signal that is time-continuous, and the receiving device includes a receiving means for receiving an audio signal and a control signal received from the transmitting means via the transmission path; a switch for switching whether or not to output the received audio signal and control signal to an audio output device; and a control for turning off the switch based on the specific control signal received by the receiving means. A voice communication system characterized by comprising means.